Alright, so I'm new to the site. Very new, but I've been reading up on the site and its creations for a bit of time now. It took me a while to actually get up the courage to try something like this, but I decided to just go through because I'm always looking to develop my writing that much more.

I decided to do a draft for a previously unclaimed number. Hopefully, this idea doesn't take from someone else's. I admit that there's some work that needs to be done, but I'm looking for some critique on what I've got.

SCP-1644-1 is to be kept in a transparent, soundproof plexiglas box measuring no more than eight (8) inches in height and four (4) inches in width.

Plexiglass is a brand, and misspelled.
Soundproofing would render the box opaque.
Try to avoid enumeration [the eight (8) thing]
We use metres here, not inches. I'm not going to bring it up every time, but remember that.

This box is to be kept in a secure soundproof containment chamber that measures 3.7 meters by 4.9 meters.

The second soundproofing is redundant, but isn't formatted so that the redundancy seems purposeful.
You also switched to metres and dropped the enumeration.

A set of sixteen (16) speakers, arranged in a configuration of four (4) speakers installed into any one wall (not including the ceiling), spaced 0.8 meters apart, are to broadcast a tone set at one-hundred fifteen decibels (115 dB) at a frequency of one-hundred twenty hertz (120 Hz) into the chamber at all times.

You just need to go back and rewrite this whole thing. There's a more concise way to phrase this.

Eyewitness accounts have noted it to be of seemingly wooden make, but further analysis dictates that the composition of the object is unidentifiable…

It is in our custody, no? Then we don't need eyewitness accounts. Also, try something more along the lines of "SCP-XXXX-1 is hypothesised to be carved [insert favourite tree here] wood, though the anomalous properties of SCP-XXXX-1 prevent further study"
That, and further analysis is impossible, which means it can't dictate anything.

…anomalous behavior does not take effect until the vibration of soundwave frequencies come in contact with its surface, after which it gains sentience. The object can pick up sounds as low as fifty decibels from up to ten feet away.

I added the bolding. Frequency is what dictates the pitch; in music, A=440 Hz. Decibels are a measurement of the amplitude of a wave function. The point I'm making is that you're comparing apples and oranges. Choose one and stick with it.

SCP-1644 will animate when it detects any soundwaves it can pick up, much like a bat would with echolocation, except in the case of containment procedures listed above.

Simile is not required, and the containment procedures are designed to prevent activation, not to be an exception to activation.

Upon identifying its target, SCP-1644-1 will attempt to manipulate its target using its limbs and head, ultimately taking control of it.

What. This is so very vague. Does the puppet wave its arms around? Physically jump on someone? Mind control? This is the anomalous property of your SCP, and it's one vague line.

The form of SCP-1644-1 has been proven to morph at will while keeping its original measurements and dimensions the same, though no reasoning has been gathered as to why.

What and why. This really adds nothing for you.

First Destruction Test

We Secure Contain and Protect, not destroy.

In attempts to follow the directive, the subject was killed by combusting inches from SCP-1644…

What? Why? Where did this come from?

TL;DR

Your measurements are inconsistent.
Containment Procedures need cleaning.
No given explanation for said Procedures. Why 120 Hz?
Tone issues.
Odd SCP powers that come out of nowhere and disappear again.
Hertz/Decibel discrepancies (that may just bother me though)
Attempted destruction of SCP
Manipulation of other SCPs by arbitrary classification

Final Opinion

I think you need to read a bit more around the site. This is… odd; your execution needs polishing.

Thank you for the critique. I needed this, as I knew there were changes that needed to be made, but didn't know exactly what needed to be changed. I'll look over what I have and format it accordingly so that it's not so poorly-written.

Having the actual number next to the word isn't necessary, it just takes up space.

Also, don't use imperial measurements, just google it if you want to convert it to metric.

A set of sixteen (16) speakers, arranged in a configuration of four (4) speakers installed into any one wall (not including the ceiling), spaced 0.8 meters apart, are to broadcast a tone set at one-hundred fifteen decibels (115 dB) at a frequency of one-hundred twenty hertz (120 Hz) into the chamber at all times.

This is awfully specific. That's not bad, but if any one of these speakers breaks or something, do bad things happen? Keep that in mind, since the Foundation's resources aren't limitless.

SCP-1644-1 is an artist's mannequin that was found in the home of artist Gregory ██████, located in Madison, Wisconsin, on 08/11/19██, after a civilian found the artist in a mangled heap on the floor and contacted the authorities [see Addendum 1644-5]

This is a long sentence, seperated with a lot of commas.

Mangled can mean different things. Was it tore up? Crushed? What, exactly?

Usually, the discovery of the SCP is saved for last. The reader came to the description to read about a, well, description.

The mannequin measures 7.2 inches tall,

Just a reminder, convert all those imperial measurements. Yeah, I grew up with Imperial too, but the US is one of the only countries that use it (there's about three others that do, all small).

Da hell do you mean by "eyewitness accounts". We have it right there in containment. Just say that it appears wooden, but it aint.

but further analysis dictates that the composition of the object is unidentifiable due to the nature of when it is approached or interacted with

Oh. So all you have to say is that it appears wooden, though that hasnt been verified.

Unapproached, it remains motionless and its anomalous behavior does not take effect until the vibration of soundwave frequencies come in contact with its surface, after which it gains sentience.

What? You start off saying that it doesn't do anything until approached, and then soundwaves come out of nowhere.

SCP-1644 will animate when it detects any soundwaves it can pick up,

You said this in the previous paragraph, I believe. I would just comment that it doesn't do anything if not approached or it doesn't sense any sound waves in the previous paragraph, and then go into what it does. Articles need organization.

"animate" is not the verb you're looking for. You mean it becomes animate.

much like a bat would with echolocation, except in the case of containment procedures listed above.

Dunno why we need to compare this to a bat. And that isn't even how echolocation works, anyhow. The animal makes the sound, and listens for it once it bounces off something.

Yeah, please clean up those previous sentences.

Upon identifying its target, SCP-1644-1 will attempt to manipulate its target using its limbs and head, ultimately taking control of it.

…Huh. So now this can pick out targets.
Don't just describe how this thing would act if it met someone, you have to describe each step with more detail; you never told me it picks out targets, I only knew it can sense vibrations.

And how does this thing control someone with its puny arms? What does it do? You don't have to tell me how it does it on a molecular level or something, just tell me what it does to control a person. (Hand motions? Dancing? What?)

On one other such occasion, it has morphed into a more detailed, female-oriented artist's mannequin (complete with upper body anatomy).

I'm sorry, but this sounded silly. Maybe ditch those parentheses, and I can take it seriously.

However, before photographic evidence could be captured, the object morphed itself back into its original state.

Do we not have surveillance systems for this thing?

SCP-1644-1 demonstrated its surprising strength by collapsing a bronze statue into dust.

Pronouns are rarely formal.

Both of those first two addendums

I feel like they belong in the description.

It's been so long since I've felt the warmth of a human body. I've missed it.

You have to think from perssonel who are writing this. Why would they put italics for the thing's dialogue? What's wrong with normal text?

Closing Statement: After communications ended, SCP-1644-1 proceeded to break the neck of D-4991 before proper containment procedures could be enforced. All further attempts to communicate with SCP-1644-1 have proven futile.

Oh. Ok. That interview log… was a thing.

First Destruction Test

Wait wait why are we destroying this We aren't the GOC buddy

The destruction of an is SCP is reserverd for only the most dire situations. This thing… it isn't too bad to contain.

Results: The woodchipper underwent a malfunction after two minutes and ceased operation. After twenty minutes of safety measures taken to ensure no on-site personnel were in immediate danger, retrieval of SCP-1644 commenced. It was found to be unharmed in any superficial fashion.

You're making this more and more powerful to me, now it's either affecting probability or invincible or something.

In attempts to follow the directive, the subject was killed by combusting inches from SCP-1644, plastering the walls with blood and various organs.

So the D-class began to burn, therefore exploding? Combust != Explode

Date of Birth: [DATA EXPUNGED]

All the expungment after this felt pointless. Expungment is only referred to sensitive or dangerous information. I don't see what's so dangerous about knowing who performed this dude's autopsy.

CAUSE OF DEATH
Unknown. Speculative theory suggests subject choked to death on blood located in the lungs.

Self-contradiction. We know how he died, just not who did it, despite how obvious it is.

Final Verdict

It's a mannequin that reacts to any sort of vibration/sound near it, and somehow takes control of the minds of living things and… what does it do?

I'm going to have to agree with Riemann. I just don't know what you're trying to make me feel from this, other than fear of being… strangled.

Please don't bump threads; we try to discourage that so we don't get spam buildup. :)

The forums tend to move rather slowly, and it can take up to a week to get multiple reviews. If you haven't already, I'd recommend trying the IRC chatroom for real-time feedback. Alternatively, you can message a staff member and ask them to direct chat attention to your thread.

This is ironically the third time I've made this post. Be patient, people. No one's getting paid for this.